Data that is read back from perpendicular magnetic recordings includes a significant amount of low frequency (DC) energy (long runs of ones (+1) or zeros (−1)). When this information passes through a read channel, the read channel tends to filter out much of this low frequency information. The long runs of 1's or 0's in user data introduce undesired low frequency components into a read channel amplifier system that is optimized for amplifying higher frequencies. Running digital sum (RDS) encoding of the user data can remove the long runs, but when RDS encoding is combined with random interleaving and turbo encoding for error correction, the RDS encoding is destroyed, and the benefits of RDS in removing low frequency components are not realized as data passes through the read/write process.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.